a. The Field of the Invention
This invention relates to the art of forming traffic regulating signs or markers on roadway pavements and, more particularly, to providing a roadway pavement with traffic regulating and facilitating means including light emitting spots that are capable of positively visualizing delineations and other signs on the surface area of such pavement.
B. The Prior Art
Traffic regulating indicia formed on roadway pavements and forming a part of the roadway area thereof, such as traffic lane dividing lines, roadway edge defining lines, pedestrian crossing areas, signalling strips and so on, are widely known, and comments are unnecessary about the importance of such indicia. The position of such indicia on the roadway surface, their shape and also their color are prescribed by traffic regulations. Traffic safety largely depends upon the fact that such indicia should be visible to the driver well far in advance of the position of the vehicle.
Various methods have been devised for providing such indicia. Conventionally, lane separations and other signs are formed by painting them on the surface of the roadway pavements. Other methods involve pouring and doctoring on said surface a layer of settable pigmented composition. An advantageous method comprises factory manufacturing a tape material adapted to be adhesively secured on the roadway pavement surface and then applying and securing the tape at the desired locations on the roadway pavement. Various procedures and machines have been proposed for expediting the forming of the desired delineation or indicium along traffic carrying roadway areas.
A vast patent literature describes several embodiments of this latter art. The U.S.A. Pat. Nos. 3,007,838, 3,235,437 and 3,262,375, of the present applicant, are a few examples of such literature relating to the application of preformed roadway pavement marking tape materials for forming the above described indicia.
The prior art has also thoroughly considered the problems involved with the visibility of the so formed indicia, and particularly at nighttime when the substantially sole source of illumination is provided solely by the vehicle headlamps, that is by a source of light, the rays of which impinge on the marker surface at spots well far in advance of the position of the vehicle, and travel in a direction which forms either a small or a very small angle with the generally planar surface of the indicium. It is known that, in such an occurrence, the visibility of the indicium is provided only by the retrocollimated rays which are reflected back essentially along their own incident rays. As a matter of fact, at the distance at which a part of an indicia on the roadway pavement would be clearly visible and unmistakably detected by the driver, the position of the source of light (the vehicle headlamps) is very close to that of the driver's eyes. These visibility problems are further aggravated by rainy weather, especially when a mirror-like film of water is formed upon the roadway surface and prevents the necessary retrocollimation.
In the U.S.A. Pat. No. 3,587,415, also of the present applicant, useful means for consistently solving at least part of the above considered problems have been described. A mode for providing retrocollimating elements of improved efficiency has been also taught by the present applicant in his U.S.A. Pat. No. 3,746,425.
It is further however known that, even by taking advantage of the most suitable and efficient light retrocollimating means, the amount of the light which can be reflected back which actually reaches the driver from a spot safely far ahead of the vehicle, is a tiny fraction of one thousandth of that emitted by the source of light on the vehicle. The light travels a distance which is twofold that of the interval between the driver's eyes and the spot in sight. The maximum length of this interval, from which the traffic safety margin largely depends, is a function of a marginal brilliancy value. This important distance will be hereinafter termed "safety visibility distance" as far as this invention is concerned.
This safety distance is acknowledgedly influenced by the transparency of the atmosphere. In hazy and, more particularly, in foggy weather, this distance is drastically reduced towards zero, and the driver can hardly follow the proper path midway of the traffic lane, as well as dangerously delaying his detection of obstructions. This poor visibility is aggravated by the same light issuing from the vehicle headlamps, because such light is scattered and refracted by the tiny water droplets which form the fog, and a dazzling "white wall" apparently faces the driver. This dazzling light, reflected by the same atmosphere, cancels the dim lights retroreflected by retrocollimating means with which the traffic regulating signs on the roadway pavement are provided.
Light emitting markers can provide a great deal better visibility. It is known that sources of light, such as aligned electric or fuel torches, are made use of for channeling and guiding traffic in emergency and in foggy weather. Illuminated traffic buttons and raised bars have been proposed and made use of. Such sources of light cannot however occupy the roadway area, nor can they properly complement the statutory indicia formed on the roadway pavements. Moreover, they cannot provide dazzling guide means which can be safely followed by drivers in poor visibility conditions.
It is therefore an object of this invention to provide a new and useful material which can be associated with a roadway pavement for providing thereon visible traffic regulating markers which are not subject to the above and other limitations and objections, thus sharply improving the traffic safety.